Weather

985 
fxus63 kmqt 062044 
afdmqt 


Area forecast discussion 
National Weather Service Marquette Michigan 
430 PM EDT Monday Oct 6 2008 


Synopsis... 
19z water vapor loop and RUC 500mb height analysis showed an intense 
looking trough off the coast of British Columbia...weak ridging 
developing downstream over the Pacific northwest...a trough stretching from 
Alberta/Saskatchewan southeast into the Central Plains...and ridging 
from the Ohio Valley northward across Upper Michigan into northern Ontario. 
Despite subsidence under the upper ridge over Upper Michigan...along with 
a dry southeast flow coming out of high pressure in eastern Ontario as 
indicated by the 12z apx sounding (40c or greater dewpoint 
depressions from 800mb up to 350mb)...warm advection clouds and precipitation 
has managed to move from northern WI into the western half of the County Warning Area. It 
should be noted that the precipitation is falling apart...likely due to the 
upper ridge still building ahead of the trough and the influence of 
the dry air. In addition...precipitation reports from automated sites in 
Upper Michigan have only been around 0.01. Some break up of the clouds 
exists over southern portions of Minnesota and WI. However...a more substantial 
area of precipitation exists along the Red River between ND and Minnesota...in an area 
of DPVA immediately ahead of the upper trough and in an axis of 
precipitable water around 1.3 inches. Dewpoints reflect the more 
moist airmass as well...with readings in the 50s over WI and 
Minnesota...with even a few low 60s as well...somewhat humid for this time 
of the year. 
&& 


Short term (tonight and tue)... 
light rain/sprinkles over the County Warning Area will dissipate this evening... 
probably before 00z...as subsidence and ridging continues to build 
over the County Warning Area ahead of the trough over the western High Plains 
inching closer. The rest of the night looks dry...with persistent 
dry southeast flow out of the high pressure area drifting off to the 
east...and ridging aloft. Therefore tonight\s only issues are clouds 
and temperatures. Cloud cover currently over the western half of the County Warning Area 
associated with warm advection/mid-level frontogenesis should slowly 
push to the northeast with time. Meanwhile...locations near the WI 
border should partially clear out. Therefore...a full cloud deck is 
not expected across any of the County Warning Area tonight...which should allow for 
some radiational cooling. However...with a southeast breeze going and 
precipitable water increasing with time to between 0.75 and 1 
inch...temperatures should not drop too much. Only change was to the 
previous forecast was to lower them a little in the inland areas of 
the eastern u.P. With mostly clear skies early. 


On Tuesday...the attention is focused to the band of showers along the 
Red River. Models are in good agreement on a slower motion compared 
to the previous forecast...likely due to the strong upper and surface 
ridging downstream. DPVA associated with the upper trough shifts 
east into the western half of the County Warning Area between 18z Tuesday and 00z Wednesday. With 
ample moisture moving in (precipitable water climbing to over an 
inch)...the DPVA should be enough to at least translate the current 
showers along the Red River eastward...reaching far Western Lake 
Superior in the morning...then into the far western u.P. In the 
afternoon. Raised probability of precipitation to likely or categorical in this area. For 
the central u... precipitation until late in the day given the 
slower timing. Temperatures are tricky since there probably will be some 
filtered sunshine through middle/high clouds in the morning. With 850mb 
temperatures prognosticated between 10-12c...high temperatures should be able to 
reach into the low to possibly middle 60s...a blend between mav and met 
guidance. Warmest readings expected in downslope southeast flow areas... 
with coolest readings downwind of Lake Michigan. If more sun occurs 
than currently expected...some locations could reach the upper 
60s...such as Pelkie. 




Long term (tue night through monday)... 


Tuesday night into Wednesday night...a middle level and surface trough moving through 
the upper Great Lakes will support precipitation into the County Warning Area. Although the 
stronger 900-600 mb fgen over northwest WI and Western Lake Superior weakens as 
it slides to the east...a broad area of 300-305k isentropic lift 
along with strong moisture inflow...bringing precipitable water values to 
1.00-1.25 inches will support decent coverage of rain with likely 
probability of precipitation included in the forecast. Any leftover rain is expected to depart 
the central County Warning Area Wednesday morning and in the afternoon over the east. A more 
zonal pattern with a middle level low and surface trough moving through northern 
Manitoba into northwest Ontario will result in dry advection with wrly 
flow. 


Thu-Mon...the global models are initially in agreement with 
pattern amplification as a trough develops over the western Continental U.S.. 
however...by the weekend into Monday significant differences develop. 
The 00z and 12z European model (ecmwf) remain slower with the progression of the middle 
level trough than the GFS and GFS ensemble mean which in addition to 
the glbl Gem push a northern stream trough through the upper lakes 
and leave a cutoff low over the SW Continental U.S.. so...with large 
uncertainty the forecast continues to lean more toward a slightly faster 
progression of the European model (ecmwf) favored by HPC. By Sat...higher probability of precipitation are 
expected over the west...closer to the inverted trough axis. 30-40 
probability of precipitation are then included through Monday to account for the large 
uncertainty. 


&& 


Aviation (for the 18z taf issuance)... 


A dry east-southeast flow around high pressure dropping south across eastern 
Ontario will maintain VFR conditions through the forecast period at 
both taf sites. However...some MVFR stratocumulus popped up this 
morning at saw...and although recent call to the site reported no 
more stratocumulus deck...decided to leave in potential for 
redevelopment during the next few hours with southeast flow off Lake Michigan 
providing upslope. 


&& 


Marine (for the 4 PM Lake Superior forecast issuance)... 


Breezy southeast winds will continue on Lake Superior tonight into much of 
Tuesday...especially on the east half...where winds speeds of up to 30 
knots are possible. The breezy winds are due to a tight pressure 
gradient between high pressure over eastern Ontario and a low pressure 
trough over far western Minnesota. This trough should be moving into far 
Western Lake Superior late Tuesday afternoon...then crossing the rest of the 
lake Tuesday night into Wednesday morning. As the trough crosses...expect 
winds to fall below 20 knots and gradually shift to the SW. For Wednesday 
into Thursday...deepening low pressure will be moving across central 
Canada to Hudson Bay...while high pressure crosses the southern 
Great Lakes. This sets up an increasing west wind over Lake 
Superior...possibly reaching up to 30 knots Wednesday night and Thursday across 
the northern portion of the lake. The high pressure area over the 
southern Great Lakes should expand up into the Lake Superior on 
Friday...bringing winds back down below 20 knots. A frontal boundary will 
then set up over the upper Great Lakes Friday night and Sat. Position 
of this boundary is uncertain...but right now it appears that southeast 
winds up to 25 knots may affect Lake Superior during this period. 


&& 


MQT watches/warnings/advisories... 


Upper Michigan...none. 
Lake Superior...none 
Lake Michigan...none. 


&& 


$$ 


Synopsis/short term...aj 
long term...jlb 
aviation...aj 
marine...aj 

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